In a database management system (DBMS) a savepoint is a designated point to which operations on a database can be rolled-back (i.e. the database can be restored to a state that existed before the operations were executed). Typically the savepoint is created before an operation that will change the database such as an insert, update or delete. The operation can comprise multiple operations. Once the operation has completed successfully the savepoint can be released.
Support for nested savepoints is a feature in some database management systems. Nesting of savepoints occurs when more than one savepoint is active at one time. Control blocks can be used to uniquely represent each of the multiple savepoints. When a savepoint is released the corresponding control block is destroyed. This approach functions adequately in a single partition or an inter-dependent partitioned database environment.
In a DBMS environment having multiple database partitions each independent of the others (i.e. shared-nothing), savepoint information must be coordinated between the database partitions and therefore the nodes associated with the partitions such as, for example, a coordinator node and a remote node. When an application of the database management system indicates that data will be modified in the database partition associated with the remote node, savepoint information stored at the coordinator node must be sent to the remote node in order to ensure coordination of the savepoints from the application's perspective. This is a potentially demanding requirement as multiple nested savepoints may exist at the coordinator node and each must be sent to the remote node. When a release savepoint request is received at the coordinator node, the request is forwarded to the remote node so that the savepoints and the corresponding control blocks can be properly maintained on the remote node as well. This too is a potentially processing intensive requirement as savepoint and control block management must be carried out for each savepoint both on the coordinator node and on the remote node.
What is needed is a apparatus and a method for releasing a nested savepoints on the remote node of a database management system that mitigates the processing intensiveness of releasing the savepoint.